Specification U.S. Pat. No. 4,864,479 (Steigerwald) discloses a DC-to-DC converter which is in the form of a full bridge. Parasitic capacitances and diodes of the switches in the full bridge provide load relief for the switches. The switches only switch on when the voltage which is applied to the switches is zero. This is referred to in the literature as “zero voltage switching” (ZVS). The functional principle described is based on a resonant process between the parasitic capacitances and the inductive component of a load resistance. Load relief for the switches can thus only be realized in a restricted range of the operating frequency. Since lamps often need to be operated in a frequency range which is prescribed by the lamp technology, and, in addition, the inductive component of the load resistance is prescribed by inductors for current limitation purposes, switching load relief is only rarely possible in the case of full bridges from the prior art during lamp operation.